Security systems are typically installed in new structures using wired communication from door and window switches to a central control unit. A common sensor for detecting an open door or window is a reed switch having a magnet on a movable member (e.g., the window frame or door frame). However, such installations are costly. When retrofitting a security system in a house or structure, wired methods are even more expensive to install because there is no easy access to the underlying wall structure.
Wireless security systems are available and also include a sensor (e.g. a reed switch and magnet) and a wireless transmitter. However, such wireless security systems require that the sensor be placed on a door or window to detect an open condition. Such sensors may be unreliable due to the wired connection to the transmitter. Additionally, the wireless transmitter requires mounting, which may be conspicuous. These systems include a transmitter that detects an open window or door via the sensor and transmits the status. Indeed, the status is transmitted for both an open and closed condition of the door or window. Moreover, the absence of the wireless signal indicates that the sensor or transmitter has been tampered with.
Detecting whether or not there is a disturbance of a portal feature, such as a window treatment or blind, is useful for safety purposes. For example, in a child safety application, a homeowner may desire a system that detects whether or not a portal feature (e.g., a window or a blind) has been disturbed, rather than one that only detects whether an intrusion has taken place. In such safety applications, a child or pet may play with or otherwise disturb a portal feature. A user (e.g., a parent or caretaker) desires to be alerted to such an event (e.g., a disturbance) so that appropriate action can be taken.